Hate is always based in ignorance and fear. Whether the fear is of one's own sexuality is possible but we cannot judge what is inside someone else. Either way, homophobia, like all predjudice and hatred, caused by some kind of fear: fear of what it means to us (or about us), fear of something we don't understand, fear of something that is unfamiliar to us, and so on. Many prejudices and the fear that inspires them has been taught from birth.
I think often those who rail the most violently against homosexuality are afraid of their own sexuality. This is not scientific or proven, it is just my opinion. And I'm not saying that all of these people are actually homosexual. What I am saying that they are afraid they might or of what would happen if they were. They are afraid of being different or judged, so they attack first before anyone can attack them.
I need to also said in post #4. Homphobia is not confined to conservatives. Nor are all liberals more self aware and tolerant. Anyone can be a homophobic no matter what their political leanings are. Anyone can be self realized no matter what their political leanings. Lets not add more judgement and division to a topic that is already cause for people to judge one another and divide the community.